Question 1

A geneticist is performing a three-point test cross in Drosophila to map three genes: A, B, and C. The observed progeny numbers are as follows: ABC (350), abc (340), Abc (45), aBC (50), ABc (60), abC (55), AbC (5), aBc (7). What is the correct order of the genes on the chromosome?

Accepted Answer

B - A - C

Question 2

Which of the following best describes the effect of DNA methylation at CpG islands in eukaryotic gene promoters?

Accepted Answer

It represses gene expression by promoting chromatin condensation.

Question 3

A partial diploid E. coli cell (merozygote) has the following genotype for the lac operon: $$I^s$$ $$O^+$$ $$Z^+$$ $$Y^+$$ / $$I^+$$ $$O^c$$ $$Z^-$$ $$Y^-. $$What will be the phenotype for $$eta-$$galactosidase production in the presence and absence of lactose?

Accepted Answer

No expression in either condition

Question 4

Which of the following chromosomal aberrations is most likely to result in a dicentric chromosome during meiosis?

Accepted Answer

Paracentric inversion

Question 5

A patient is diagnosed with Fragile X syndrome. Which of the following best describes the molecular cause of this disorder?

Accepted Answer

A trinucleotide repeat expansion in the FMR1 gene

Question 6

Which DNA repair mechanism is responsible for correcting thymine dimers caused by UV light in E. coli, and what enzyme is involved?

Accepted Answer

Photoreactivation repair; photolyase

Question 7

In the context of the Luria–Delbrück fluctuation test, what conclusion can be drawn from the observation that the number of resistant bacterial colonies varies greatly between replicate cultures?

Accepted Answer

Mutations occur randomly prior to selection.

Question 8

Which of the following statements about the yeast GAL system is correct?

Accepted Answer

GAL4 is a regulatory protein that activates transcription in the presence of galactose.

Question 9

A child is born with Down syndrome due to a Robertsonian translocation. Which of the following statements is TRUE regarding the inheritance of this condition?

Accepted Answer

It can be inherited from a phenotypically normal parent carrying a balanced translocation.

Question 10

Which of the following best describes the function of riboswitches in bacterial gene regulation?

Accepted Answer

They are mRNA regions that bind metabolites to regulate gene expression.

Question 11

A mutation changes a codon from UAU (tyrosine) to UAA (stop). What type of mutation is this, and what is the likely effect on the protein?

Accepted Answer

Nonsense mutation; results in a truncated protein

Question 12

Which of the following is a key finding of the ENCODE project?

Accepted Answer

A large proportion of the genome is transcribed and has regulatory functions.

Question 13

Which of the following best explains why allopolyploid plants are often fertile while their hybrid parents are sterile?

Accepted Answer

Allopolyploids have balanced sets of chromosomes that can pair during meiosis.

Question 14

Which of the following is TRUE regarding the use of microarray analysis in genetic research?

Accepted Answer

It measures gene expression levels across thousands of genes simultaneously.

Question 15

A researcher uses the Ames test to evaluate a new chemical. After exposure, the number of His$$^+$$ revertant colonies increases significantly compared to the control. What does this indicate?

Accepted Answer

The chemical induces mutations that restore histidine synthesis.

Question 16

Which of the following statements about DNA transposons is correct?

Accepted Answer

They move by a cut-and-paste mechanism using transposase.

Question 17

Which of the following best describes the difference between bulk RNA sequencing and single-cell RNA sequencing?

Accepted Answer

Single-cell RNA-seq reveals cellular heterogeneity within tissues, while bulk RNA-seq provides average expression levels.

Question 18

Which of the following is a consequence of a pericentric inversion during meiosis?

Accepted Answer

Production of gametes with duplications and deficiencies, but all chromatids retain a centromere

Question 19

Which of the following best describes the outcome of the ACLU court case against Myriad Genetics regarding BRCA1/2 gene patents?

Accepted Answer

The Supreme Court ruled that naturally occurring human genes cannot be patented.

Question 20

Which of the following best explains how gene drives are used to combat Zika virus transmission in mosquito populations?

Accepted Answer

By inserting a lethal gene that is inherited at a higher-than-Mendelian rate

Comprehensive Study Guide: Linkage, Gene Regulation, Chromosomal Mutations, Mutation & Repair, and Genetic Engineering Applications

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